Musty smelling basement with a floating floor

TSullivan

I have a beautiful finished basement with a floating floor. When I open the door to the basement it smells musty primarily in the stairwell. It doesn't smell musty under the floating floor when we open up to check the sump pump. It is ventilated with a fan and it doesn't smell musty when you smell the air outside blowing from under the floating floor. What could be causing the smell and what do I do?

oodssoo

Do you have carpet on the steps of the stairs to the basement?

How old is the house?

How long has it been "musty"?

What do you have stored under the stairs - in the space under the stairs?

weekendwarrior9

is the stairwell enclosed or open? I had a sealed staircase that rodents chewed a hole into. A cat got in there and died. Then the rats ate the cat. When I found it, there was the dis-articulated cat, several dead rats, and about a centimeter of solid rat feces. And a bunch of chewed walnut husks.

Moral of story: an enclosed stairwell can hold all sorts of surprises.

allthumbsdiy

that is one crazy story. since i don't like finding dead things, i should open up my staircase!

re: musty smell, i had a very small leak towards the end of the wall (bottom of the stairs) that went undetected for awhile. you may want to check that area

weekendwarrior9

Even better was my bathtub. When we bought the place, I knew bathroom had rot, water was leaking 'cause the drain wasn't connected. So there we were taking stuff apart and went to lift up the bathtub.

I kid you not, walnut husks poured out of the bathtub walls (one of those hollow walled built-in dealios), out of the stud bays, everywhere. That scene from Lord of the Rings, the skull avalanche? That was us, with walnuts.

Entire generations, nay, dynasties of squirrels had been busy packing walnuts under the tub, in the tub walls, then into the stud bays floor to ceiling.

I filled five and a half contractor bags full of walnuts that weekend.

Later, when we tore down the ceiling, yup, ceiling joist bays were full over the bathroom too.

gobug

Mildew and other fungi will grow in cement. That you have a sump pump indicates the water level is close to the bottom of the basement. My suspicion is that even though you are using your sump pump and don't smell mildew when you check it and other air from beneath the slab, you have mildew living in the slab. This is usually visible as a thin layer of white powdery stuff on the surface of the cement. Due to the porosity of the cement, it is likely living through the slab, not just on the surface.

A disenfectant will kill it, but not eliminate it as a potential problem. If it is limited to one area, perhaps the "french drain" is not working well enough in that area. One suggestion is to drill a small hole through the slab in the area where you smell your problem. The slab is probably too thick to use a garden moisture meter, but a GFCI extention cord and a drill will ground fault if the ground is moist beneath the slab. That will happen when you drill the hole through the slab.

Good luck. Molds and fungi can be dangerous.

TSullivan

We store dry things like a card table and chairs, tornado shelter stuff in plastic.

Thanks.

TSullivan

Thanks.

TSullivan

Thank You.

TSullivan

Thank you for this information. It is very helpful. As I was reading your post I realized our sprinkler system main box is behind this wall but higher and even though it is not leaking from the above ground pipes I wonder if that is not the culprit. What would I do, dig down at the house foundation to check for a leak at the stairwell level or do you think I could use a moisture meter in the stairwell outside wall to check? How do you know what moisture is okay or not. Thanks.

techpappy

may simply be condensation in box..may have to insulate or relocate piping ...should be able to use moisture meter at inside wall to see if there is excess moisture in wall near smell..

gobug

The biggest question in my mind is first where is the source of the musty odor? That should provide clues to what you need to do to alter the scenario.

At first I thought maybe your french drain has a low spot near the bad smell area. If so, I think the musty odor would be present in the sump pit. That would be difficult ($wise) to fix.

Since you do not have an odor in the sump pit, the musty odor could be coming from the ground, against the house, above the sump pit level, near the odor. This could be from under a porch or driveway. I suggest that you study the flow of ground water (roof drains, ground slopes, connections to public plumbing, etc) Maybe that will add something of importance to your thoughts.

I recently had a job (for bugs) and the old old house had a musty odor in the crawl space. I could not find any damp soil or mold in that crawl space. The owner later found out that there was an old sewage vent pipe that was open inside a wall rather than going out through the roof. It took more than a year to find the source of the musty odor. Fixing it solved health concerns, and was cheap (materials). I don't know how he found it.

Good luck, don't give up.
Gary

bdwilliams

I installed a floating floor in my basement and had to remove it because of the smell. From what I have gathered from various contractors, floating floors should only be used in basements that are BONE DRY. Even the slightest bit of moisture will cause mildew and mold to grow.